Water-Soluble Conductive Composite Binder for High-Performance Silicon Anode in Lithium-Ion Batteries

The design of novel and high-performance binder systems is an efficient strategy to resolve the issues caused by huge volume changes of high-capacity anodes. Herein, we develop a novel water-soluble bifunctional binder composed of a conductive polythiophene polymer (PED) and high-adhesive polyacrylic acid (PAA) with abundant polar groups. Compared with conventional conductive additives, the flexible conductive polymer can solve the insufficient electrical contact between active materials and the conductive agent, thus providing the integral conductive network, which is extremely important for stable electrochemical performance. Additionally, the polar groups of this composite binder can form double H-bond interactions with the hydroxyl groups of SiO2 layers onto the silicon surface, keeping an integral electrode structure, which can decrease the continuous formation of SEI films during the repeated cycles. Benefiting from these bifunctional advantages, the Si electrodes with the composite binder delivered a high reversible capacity of 2341 mAh g(-1) at 1260 mA g(-1), good cycle stability with 88.8% retention of the initial reversible capacity over 100 cycles, and high-rate capacity (1150 mAh g(-1) at 4200 mA g(-1)). This work opens up a new venture to develop multifunctional binders to enable the stable operation of high-capacity anodes for high-energy batteries.